A conventional article of footwear generally includes two primary elements: an upper and a sole structure. The upper is secured to the sole structure and forms a void within the article of footwear for comfortably and securely receiving a foot. The sole structure is secured to a lower surface of the upper so as to be positioned between the upper and the ground. In some articles of athletic footwear, for example, the sole structure may include a midsole and an outsole. The midsole may be formed from a polymer foam material that attenuates ground reaction forces to lessen stresses upon the foot and leg during walking, running, and other ambulatory activities. The outsole is secured to a lower surface of the midsole and forms a ground-engaging portion of the sole structure that is formed from a wear-resistant material.
The upper of the article of footwear generally extends over the instep and toe regions of the foot, along the medial and lateral sides of the foot, and around the heel region of the foot. Access to the void on the interior of the upper is generally provided by an ankle opening in a heel region of the article of footwear. A lacing system is often incorporated into the upper to adjust the fit of the upper, thereby facilitating entry and removal of the foot from the void within the upper. In addition, the upper may include a tongue that extends under the lacing system to enhance adjustability of the article of footwear, and the upper may incorporate a heel counter to limit movement of the heel.